A servo motor is an electromagnetic mechanical device for electromechanical energy conversion, and its main feature is that the output torque or speed can be controlled rapidly and accurately. According to different requests for utilization and power supplies, servo motors can be classified into different categories, such as a direct current servo motor, an alternating current synchronous servo motor, an alternating current induction servo motor and the like.
The direct current servo motor has the advantages of good speed adjustability, high starting torque and simple control system, but it also has complicated structure, high manufacturing cost, high maintenance cost and poor reliability.
The alternating current synchronous servo motor has two structural forms. The first structural form is an alternating current permanent magnet synchronous servo motor. And its rotor produces a high-density permanent magnetic field through the use of permanent magnetic materials or scarce rare earth resources. The second structural form is an alternating current winding rotor synchronous servo motor. Its rotor produces a magnetic field by an additional excitation supply, where the current is introduced through a slip ring, which causes complicated structure, high manufacturing cost and high maintenance cost.
The alternating current induction servo motor is also called as an alternating current asynchronous servo motor. It is simple in structure, easy for manufacture and with high reliability, but the motor has serious defects of complicated controller, poor low-speed torque characteristic and low control precision.
The present invention discloses a novel induction servo motor with a constant-output-force or a constant-output-torque by using uniform magnetic fields, which is based on a new design principle and can be classified into two types: a rotary-type induction servo motor with a constant-output-torque by using uniform magnetic fields and a linear-type induction servo motor with a constant-output-force by using uniform magnetic fields. Wherein, the linear-type induction servo motor with a constant-output-force by using uniform magnetic fields is a variation form of the rotary-type induction servo motor with a constant-output-torque by using uniform magnetic fields. And the most important difference between the novel motor and an existing alternating current servo motor is that the novel motor employs uniform magnetic fields rather than rotating magnetic fields or travelling wave magnetic fields. And the main advantages of the novel motor are as follows: firstly, it has no wearing parts like slip rings, so the maintenance cost is low; secondly, the stator (primary part) has simple winding forms and structures, and the rotor (secondary part) does not adopt permanent magnetic materials, therefore, the manufacturing cost is low; thirdly, the novel motor can be powered by a fixed frequency alternating current, and the output torque or output force required can be accurately controlled by simply adjusting the voltage magnitude of the power supply; finally, its control system does not adopt a vector control principle of the existing alternating current induction servo motor, because the power supply at a fixed frequency is adopted to power the novel induction servo motor, its control system is similar to a control system of the direct current servo motor and is simple in design.
So far, No any relevant report, literature or patent is published in China and abroad with respect to the present invention: a novel induction servo motor with a constant-output-force or a constant-output-torque by using uniform magnetic fields.